1) Field of the Invention
The present invention relates to an optical apparatus and an optical cross connect apparatus.
2) Description of the Related Art
Optical communication systems nowadays use a wavelength division multiplexing (WDM) communication technique to assure a high transmission capacity. Further, commercialization of an optical cross connect node and a optical add/drop multiplexing node wherein switching is performed using an optical wavelength as a changeover unit in a hub node to which transmission path fibers are concentrated in a communication system or a line branching and inserting node in a ring network is proceeding.
Conventionally, such apparatus as described above have been formed such that, for example, as shown in FIG. 18, discrete parts such as a wavelength demultiplexer 901, an optical switch 902, a variable optical attenuator 903, a wavelength multiplexer 904 and so forth are mounted in individual units. An apparatus disclosed in Japanese Patent Laid-Open No. 2001-16625 (hereinafter referred to as Patent Document 1) is an example wherein discrete parts are mounted as units independent of each other as described above.
At present, in order to achieve miniaturization of an apparatus, also incorporation of a wavelength selective type optical switch (WSS: Wavelength Selective Switch) to which the functions described above are integrated is proceeding. FIG. 19 shows an optical cross connection apparatus 910 as an example which is configured using such a wavelength selective switch as just described. The optical cross connect apparatus 910 shown in FIG. 19 can change over the output routes of WDM input light inputted from n input ports #11 to #1n to n output ports #21 to #2n for each wavelengths and output the switched WDM light as WDM output light through the output ports #21 to #2n. 
In the optical cross connect apparatus 910, a plural number of wavelength selective switches (1×n wavelength selective switches) 911 to 91n individually having one input and n outputs are provided on the input port side, the number corresponding to that of the input ports. Further, a plural number of n×1 wavelength selective switches 921 to 92n are provided on the output port side, the number corresponding to that of the output ports. Further, the optical cross connect apparatus 910 is formed such that outputs of the wavelength selective switches 911 to 91n are individually connected to inputs of the wavelength selective switches 921 to 92n. 
In such an optical cross connect apparatus 910 as shown in FIG. 19, if a fault occurs with any of the discrete parts or the like in the wavelength selective switches 911 to 91n and 921 to 92n, then even if the parts other than the part with which the fault occurs operate normally, replacement of each of the wavelength selective switches 911 to 91n and 921 to 92n in which the faulty parties included must be performed.
Particularly, where, as seen in FIG. 20, a fault occurs, in the wavelength selective switches 911 to 91n and 921 to 92n, only with a switch for an optical signal having a particular wavelength within WDM light [for example, an optical signal having a wavelength λ1 within a WDM optical signal formed from wavelengths λ1 to λ8, refer to (a) of FIG. 20] or a fault occurs only with switching operation for a specific output route [refer to (b) of FIG. 20], even if switching operation for the other wavelengths or the other output routes is performed regularly, the wavelength selective switches which form one unit must be replaced entirely.
Accordingly, in such an optical cross connect apparatus 910 as shown in FIG. 19, a configuration wherein the apparatus 910 can be restored from a fault without waiting replacement of a unit upon occurrence of such a fault as described above is required as a subject. Further, a method wherein, when such replacement of a unit as described is performed, the influence on the other connections which operate normally is suppressed to the utmost is required as a subject.